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Hierarchical Virtual Trunking Over Packet Networks - Patent 7944817

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United States Patent: 7944817


































 
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	United States Patent 
	7,944,817



 Sylvain
 

 
May 17, 2011




Hierarchical virtual trunking over packet networks



Abstract

 The present invention establishes reserved paths between nodes in a
     central packet network and in local networks attached to the central
     network. Each reserved path has a defined bandwidth and may be
     implemented as an LSP in an MPLS network or as a PVC in an ATM network.
     Associated with each reserved path is a virtual trunk group representing
     the same bandwidth as the virtual path. Telephony calls requiring media
     flows associated with a channel in the virtual trunk group will transport
     packets along the reserved path associated with the virtual trunk group.
     Access to the reserved path is limited to telephony media flows
     associated with a virtual trunk group to ensure adequate bandwidth at all
     times for the number of channels associated with the virtual trunk group.
     Backup reserved paths may be associated with the primary reserved path to
     provide the necessary redundancy required for voice-based telephony
     applications.


 
Inventors: 
 Sylvain; Dany (Gatineau, CA) 
 Assignee:


Nortel Networks Limited
 (Mississauga, Ontario, 
CA)





Appl. No.:
                    
10/266,183
  
Filed:
                      
  October 7, 2002

 Related U.S. Patent Documents   
 

Application NumberFiling DatePatent NumberIssue Date
 60367676Mar., 2002
 

 



  
Current U.S. Class:
  370/228  ; 370/352; 370/392; 370/397; 370/401; 370/409; 709/239
  
Current International Class: 
  H04L 12/28&nbsp(20060101); H04L 12/56&nbsp(20060101); H04L 12/26&nbsp(20060101); H04L 12/66&nbsp(20060101); G06F 15/173&nbsp(20060101)
  
Field of Search: 
  
  











 370/229,389,230,352,469,443,228,392,397,401,409 709/239
  

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He et al.



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EP



   
 Other References 

International Search Report for PCT/IB03/00861 mailed Jul. 16, 2003. cited by other.  
  Primary Examiner: Hsu; Alpus H


  Assistant Examiner: Hassan; Saad


  Attorney, Agent or Firm: Withrow & Terranova, PLLC



Parent Case Text



 This application claims the benefit of provisional patent application
     Ser. No. 60/367,676, filed Mar. 26, 2002, the disclosure of which is
     hereby incorporated by reference in its entirety.


CROSS-REFERENCE TO RELATED APPLICATIONS


 The present application is related to U.S. application Ser. No.
     10/175,122 filed Jun. 19, 2002, currently pending, the disclosure of
     which is incorporated herein by reference, in its entirety.

Claims  

What is claimed is:

 1.  A method comprising: a) establishing a central reserved path having a defined bandwidth between two local edge routers, each of which provide a point of ingress and a
point of egress for corresponding local networks;  b) defining a central virtual trunk group having the defined bandwidth;  c) associating the central virtual trunk group with the central reserved path such that calls within the central virtual trunk
group are carried over the central reserved path;  d) establishing local reserved paths between internal edge routers in the local networks and the local edge routers in the local networks;  e) defining a local virtual trunk group;  and f) associating
the local virtual trunk group with at least one local reserved path of the local reserved paths such that calls within the local virtual trunk group are carried over the at least one local reserved path.


 2.  The method of claim 1 further comprising: g) defining a plurality of local virtual trunk groups;  h) providing individual media flows for each call between each internal edge router and media gateways associated with the internal edge
routers;  and i) assigning the individual media flows to the plurality of local virtual trunk groups to facilitate communications between the media gateways and the local edge routers in part via the local reserved paths between the local edge routers
and the internal edge routers.


 3.  The method of claim 1 further comprising: g) associating a plurality of media gateways with the internal edge routers, the media gateways providing an interface for circuit-switched communications to form a node;  and h) providing call
processing for calls handled by the media gateways with a media gateway controller associated with the node.


 4.  The method of claim 1 wherein the central reserved path is a label switched path provided by an MPLS network, and the local edge routers are label edge routers.


 5.  The method of claim 1 wherein the central reserved path is an ATM permanent virtual circuit.


 6.  The method of claim 1 further comprising providing a plurality of hierarchically layered networks having edge routers connected by reserved paths and associating virtual trunk groups with the reserved paths.


 7.  The method of claim 1 further comprising establishing a plurality of central reserved paths between a plurality of pairs of local edge routers and defining a central virtual trunk group for each of the plurality of central reserved paths to
form a mesh of virtual trunk groups.


 8.  The method of claim 7 wherein all calls supported by the central virtual trunk group are carried over a shared path provided by the central reserved path.


 9.  A method comprising: a) establishing a central reserved path having a defined bandwidth between two local edge routers, each of which provide a point of ingress and a point of egress for corresponding local networks;  b) defining a central
virtual trunk group having the defined bandwidth;  c) associating the central virtual trunk group with the central reserved path such that calls within the central virtual trunk group are carried over the central reserved path;  and d) providing call
processing for the calls handled by the local edge routers with associated call controllers.


 10.  A method comprising: a) establishing a central reserved path having a defined bandwidth between two local edge routers, each of which provide a point of ingress and a point of egress for corresponding local networks;  b) defining a central
virtual trunk group having the defined bandwidth;  and c) associating the central virtual trunk group with the central reserved path such that calls within the central virtual trunk group are carried over the central reserved path, wherein the central
virtual trunk group is defined to support a set number of the calls at any given time based on the defined bandwidth and further comprising defining a limited number of the calls for the central virtual trunk group based on the set number of calls.


 11.  A method comprising: a) establishing a central reserved path having a defined bandwidth between two local edge routers, each of which provide a point of ingress and a point of egress for corresponding local networks;  b) defining a central
virtual trunk group having the defined bandwidth;  c) associating the central virtual trunk group with the central reserved path such that calls within the central virtual trunk group are carried over the central reserved path;  and d) establishing a
reserved backup path having the defined bandwidth between the two local edge routers.


 12.  The method of claim 11 further comprising: d) detecting a failure of the central reserved path;  and e) associating the central virtual trunk group with the reserved backup path such that calls within the central virtual trunk group are
carried over the reserved backup path when the failure is detected.


 13.  The method of claim 12 further comprising: f) providing a heartbeat signal along the central reserved path;  g) monitoring the heartbeat signal;  and h) triggering the association of the central virtual trunk group with the reserved backup
path if the heartbeat signal is not detected.


 14.  The method of claim 11 further comprising distributing loads associated with calls supported by the central virtual trunk group among the central reserved path and the reserved backup path when the central reserved path and the reserved
backup path are operational.


 15.  A node comprising: a) a local edge router terminating one end of a central reserved path having a defined bandwidth and extending to another local edge router and terminating one end of a local reserved path and extending to an internal
edge router in an associated local network;  and b) a call controller facilitating call control with another call controller associated with the central reserved path wherein a central virtual trunk group having the defined bandwidth is associated with
the central reserved path such that calls within the central virtual trunk group are carried over the central reserved path via the local edge router.


 16.  The node of claim 15 wherein a local virtual trunk group having a second defined bandwidth is associated with the local reserved path such that the calls within the local virtual trunk group are carried over the local reserved path via the
local edge router.


 17.  The node of claim 16 wherein the local virtual trunk group is defined to support a set number of calls at any given time based on the second defined bandwidth.


 18.  The node of claim 15 wherein the central virtual trunk group is defined to support a set number of calls at any given time based on the defined bandwidth.


 19.  The node of claim 15 wherein the central reserved path is an MPLS label switched path and the local edge router is a label edge router.


 20.  The node of claim 19 wherein the local reserved path is an MPLS label switched path.


 21.  The node of claim 19 wherein the central reserved path is an ATM permanent virtual circuit.


 22.  The node of claim 15 wherein a plurality of hierarchically layered networks are provided having edge routers connected by reserved paths and having associated virtual trunk groups with the reserved paths.


 23.  The node of claim 15 wherein a reserved backup path is established having the defined bandwidth between the two local edge routers.


 24.  The node of claim 23 wherein the local edge router is adapted to: c) detect a failure of the central reserved path;  and d) associate the central virtual trunk group with the reserved backup path such that the calls within the central
virtual trunk group are carried over the reserved backup path when the failure is detected.


 25.  The node of claim 23 wherein the local edge router is further adapted to: c) provide a heartbeat signal along the central reserved path;  d) monitor the heartbeat signal;  and e) trigger the association of the central virtual trunk group
with the reserved backup path if the heartbeat signal is not detected.


 26.  The node of claim 23 wherein loads associated with the calls supported by the central virtual trunk group are distributed among the central reserved path and the reserved backup path when the central reserved path and the reserved backup
path are operational.


 27.  A system comprising: a) means for establishing a central reserved path having a defined bandwidth between two local edge routers, each of which provide a point of ingress and a point of egress for corresponding local networks;  b) means for
defining a central virtual trunk group having the defined bandwidth;  c) means for associating the central virtual trunk group with the central reserved path such that calls within the central virtual trunk group are carried over the central reserved
path;  d) means for establishing local reserved paths between internal edge routers in the local networks and the local edge routers in the local networks;  e) means for defining a local virtual trunk group;  and f) means for associating the local
virtual trunk group with at least one local reserved path of the local reserved paths such that calls within the local virtual trunk group are carried over the at least one local reserved path.


 28.  The system of claim 27 further comprising: g) means for defining a plurality of local virtual trunk groups;  h) means for providing individual media flows for each call between each internal edge router and media gateways associated with
the internal edge routers;  and i) means for assigning the individual media flows to the plurality of local virtual trunk groups to facilitate communications between the media gateways and the local edge routers in part via the local reserved paths
between the local edge routers and the internal edge routers.


 29.  The system of claim 27 further comprising: g) means for associating a plurality of media gateways with the internal edge routers, the media gateways providing an interface for circuit-switched communications to form a node;  and h) means
for providing call processing for calls handled by the media gateways with a media gateway controller associated with the node.


 30.  The system of claim 27 further comprising means for providing call processing for the calls handled by the local edge routers with associated call controllers.


 31.  The system of claim 27 wherein the central virtual trunk group is defined to support a set number of the calls at any given time based on the defined bandwidth and further comprising means for defining a limited number of the calls for the
central virtual trunk group based on the set number of calls.


 32.  The system of claim 27 wherein the reserved path is a label switched path provided by an MPLS network, and the local edge routers are label edge routers.


 33.  The system of claim 27 wherein the reserved path is an ATM permanent virtual circuit.


 34.  The system of claim 27 further comprising means for establishing a plurality of central reserved paths between a plurality of pairs of local edge routers and means for defining a central virtual trunk group for each of the plurality of
central reserved paths to form a mesh of virtual trunk groups.


 35.  The system of claim 34 wherein all calls supported by the central virtual trunk group are carried over a shared path provided by the central reserved path.


 36.  The system of claim 27 further comprising means for establishing a reserved backup path having the defined bandwidth between the two local edge routers.


 37.  The system of claim 36 further comprising: d) means for detecting a failure of the central reserved path;  and e) means for associating the central virtual trunk group with the reserved backup path such that calls within the central virtual
trunk group are carried over the reserved backup path when the failure is detected.


 38.  The system of claim 37 further comprising: f) means for providing a heartbeat signal along the central reserved path;  g) means for monitoring the heartbeat signal;  and h) means for triggering the association of the central virtual trunk
group with the reserved backup path if the heartbeat signal is not detected.


 39.  The system of claim 36 further comprising means for distributing loads associated with calls supported by the central virtual trunk group among the central reserved path and the reserved backup path when the central reserved path and the
reserved backup path are operational.  Description  

FIELD OF THE INVENTION


 The present invention relates to telecommunications, and in particular to ensuring quality of service levels over packet networks.


BACKGROUND OF THE INVENTION


 There is a growing interest in the convergence of the public switched telephone network (PSTN), the Internet and other internets and intranets.  The convergence of these networks requires technology that facilitates interworking in a uniform and
effective manner.  The next generation of unified networks will provide an open and scalable architecture to accommodate multiple vendors and protocols under a common packet network.  At the moment, there are several obstacles to providing telephony
services on a packet network with the same level of performance and availability as is available on the PSTN today.


 The traditional PSTN provides constant bandwidth streams of information between users.  These media streams travel over dedicated circuits.  On the other hand, packet networks have been prone to packet loss and delays, which affect the quality
of streaming media required to carry voice communications.  Given the high quality levels associated with the PSTN, subscribers expect and demand traditional quality regardless of the transmission medium.


 The bursty nature of packet communications makes controlling communication quality and ensuring sufficient bandwidth very difficult.


 The bursty nature of packet communications makes controlling communication quality and ensuring sufficient bandwidth very difficult.  Traditional "fat pipe" models, which rely on the overall network to find a way to transmit the packets with the
required quality of service levels, have not been completely successful.  Further, the integration of call processing for the PSTN and packet networks has proven difficult to manage.


 Given the desire to use packet networks as the centerpiece for telephony communications, there is a need for a way to ensure quality of service levels for telephony communication carried at least in part over packet networks and provide call
processing in a uniform manner.


SUMMARY OF THE INVENTION


 The present invention establishes reserved paths between nodes in a central packet network and in local networks attached to the central network.  Each reserved path has a defined bandwidth and may be implemented as a label switched path (LSP)
in a multiprotocol label switched (MPLS) network or as a permanent virtual circuit (PVC) in an asynchronous time multiplexing (ATM) network.  Associated with each reserved path is a virtual trunk group representing the same bandwidth as that of the
virtual path.  Telephony calls requiring media flows associated with a channel in the virtual trunk group will transport packets along the reserved path associated with the virtual trunk group.  Access to the reserved path may be limited to only
telephony media flows associated with a virtual trunk group to ensure adequate bandwidth at all times for the number of channels associated with the virtual trunk group.  Backup reserved paths may be associated with the primary reserved path to provide
the necessary redundancy required for voice-based telephony applications.


 The invention provides for a hierarchical network infrastructure wherein a network of reserved paths may be established at each network level, and access between network levels is provided by an access node that terminates reserved paths on the
connection networks.  As such, the infrastructure is infinitely scalable and may support two or more network layers in an efficient and easy to manage manner.


 Those skilled in the art will appreciate the scope of the present invention and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing
figures. 

BRIEF DESCRIPTION OF THE DRAWING FIGURES


 The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the invention, and together with the description serve to explain the principles of the invention.


 FIG. 1 provides a high level overview of a communication network infrastructure according to one embodiment of the present invention.


 FIG. 2 is a block representation of a local network infrastructure according to one embodiment of the present invention.


 FIG. 3 is a block representation of a media gateway controller according to one embodiment of the present invention.


 FIG. 4 is a block representation of a media according to one embodiment of the present invention.


 FIG. 5 is a block representation of an edge router according to one embodiment of the present invention.


 FIG. 6 illustrates a label switched path in the local network infrastructure according to one embodiment of the present invention.


 FIG. 7 illustrates a virtual trunk group assigned to the label switch path of FIG. 6 according to one embodiment of the present invention.


 FIG. 8 illustrates a network mesh configuration in the local network infrastructure according to one embodiment of the present invention.


 FIG. 9 illustrates backup label switched paths for the mesh illustrated in FIG. 8 according to one embodiment of the present invention.


 FIG. 10 illustrates an access node associated with the mesh illustrated in FIG. 8 and providing access to a central network.


 FIG. 11 is a block representation of a local edge router for an access node according to one embodiment of the present invention.


 FIG. 12 is a block representation of a call controller according to one embodiment of the present invention.


 FIG. 13 is a block representation of the communication network infrastructure illustrated in FIG. 1 according to one embodiment of the present invention.


 FIG. 14 illustrates backup label switched paths for the communication network infrastructure illustrated in FIG. 13 according to one embodiment of the present invention.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS


 The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the invention and illustrate the best mode of practicing the invention.  Upon reading the following description in light of the
accompanying drawing figures, those skilled in the art will understand the concepts of the invention and will recognize applications of these concepts not particularly addressed herein.  It should be understood that these concepts and applications fall
within the scope of the disclosure and the accompanying claims.


 The present invention establishes reserved paths between nodes in a packet network.  Each reserved path has a defined bandwidth.  Associated with each reserved path is a virtual trunk group.  The virtual trunk group has the same bandwidth as the
reserved path and supports a set number of channels.  Telephony calls requiring media flows associated with a channel in the virtual trunk group will transport packets along the reserved path associated with the virtual trunk group.  Access to the
reserved path may be limited to only media flows associated with a virtual trunk group to ensure adequate bandwidth at all times for the number of channels associated with the virtual trunk group.  Backup reserved paths may be associated with the primary
reserved path to provide the necessary redundancy required for voice-based telephony applications.


 With reference to FIG. 1, a communication environment 2 is shown where numerous local networks 4 support media flows for select regions or localities.  Media flows within a given region are supported inside the respective local network 4 on
reserved paths contained within the local network 4.  Media flows crossing a central network 6 between devices on different ones of the local networks 4 are supported by inter-network (central) reserved paths 8, which extend between access nodes 10.  In
general, a reserved path architecture with the local networks 4 is similar to that for the central network 6.  As such, the following description initially describes the reserved path architecture for the local networks 4, then describes how the local
networks 4 access the central network 6, and concludes by describing the reserved path architecture for the central network 6.


 Turning now to FIG. 2, a local network 4 is centered about a core packet network 12 having numerous routers 14 interconnected to facilitate the routing of packets between edge routers 16.  The edge routers 16 act as the ingress and egress points
for associated media gateways 18 to the core network 12.  The media gateways 18 provide a packet interface for circuit-switched telephony devices, such as telephones 20 or circuit-switched trunks (not shown).  Media gateway controllers 22 are associated
with and effectively control groups of media gateways 18.  As illustrated, an edge router 16 may be associated with a group of media gateways 18 and a call controller, such as a media gateway controller 22, to form a node 24.  There are three nodes 24
illustrated in FIG. 1, referenced as A, B, and C. The media gateway controllers 22 may communicate with each other to facilitate call control between media gateways 18 in different nodes 24, or may cooperate with the call control entities of an
intelligent network (IN) of the public switched telephone network (PSTN) 26 and other networks.


 To facilitate interworking of circuit-switched and packet communications, there are two primary elements: a media gateway 18 and a media gateway controller 22.  The media gateway 18 provides the actual interface between the packet network
associated with an edge router 16 and the telephony devices, such as telephones 20, or circuit-switched telephony interfaces such as circuit-switched trunks (not shown).  The media gateway controller 22 provides decision-making and coordination between
media gateways 18 to facilitate interworking, alone or in association with other media gateway controllers 22 or the call control services of the PSTN 26.


 The primary responsibility of a media gateway 18 is to allow traditional telephony media, such as voice, to be transported in a packet network using an Internet Protocol (IP) asynchronous transfer mode (ATM) format, and other formats are
possible.  The media gateways 18 allow media to move without loss of integrity or quality between networks and network technologies.  In essence, the media gateways 18 provide a bi-directional interface between disparate networks, and typically, between
a traditional circuit-switched telephony network and a packet network.


 For the purpose of describing the preferred embodiments of the present invention, the following description assumes the media gateways 18 provide a bi-directional interface between a circuit-switched network, such as the TDM-based PSTN networks,
and packet networks coupled to the edge routers 16.  For example, a media gateway 18 may implement high-speed TDM trunk interfaces or line interfaces, which are commonly used interfaces between switching elements in a circuit-switched network; however,
other interfaces are possible.


 The primary responsibilities of the media gateway controller 22 are to make decisions based on flow-related information and to provide instructions on interconnecting elements or endpoints within and throughout the networks.  Media gateway
controllers 22 store status information on media flows and may be used to generate administrative records for a variety of media-related activities, such as billing.  Most prominently, media gateway controllers 22 provide coordination of media gateways
18.  Typically, media gateway controllers 22 direct media gateways 18 to set up, handle, and end individual media flows, which will take place between the respective media gateways 18.


 Referring now to FIG. 3, a block schematic of a media gateway controller 22 is shown having a central processing unit (CPU) 28 containing memory 30 and the requisite software 32 for operation.  The media gateway controller 22 will have at least
one interface, preferably a packet interface 34 capable of communicating with other media gateway controllers 22 and the associated media gateways 18.  To establish such communications, the media gateway controllers 22 associated with the media gateways
18 supporting the telephones 20 cooperate with one another and the media gateways 18 to establish the communication sessions.


 Turning now to FIG. 4, a block schematic of a media gateway 18 is shown having a CPU 36 containing memory 38 and the requisite software 40 for operation.  The CPU 36 operates to provide a bi-directional interface between one or more packet
interfaces 42 and a media interface 44.  The media interface 44 is the interface opposite the packet network, and is preferably a circuit-switched interface supporting traditional trunks and lines of a traditional, circuit-switched telephone network. 
When interfacing with traditional telephony equipment, the media interface 44 is typically configured to handle TDM communications or any other analog or digital data streams required to facilitate such communications.  The media interface 44 may be a
line interface supporting a telephone 20, as shown in FIG. 2.


 FIG. 5 is a block schematic of an edge router 16 having a CPU 46 with associated memory 48 and the requisite software 50 for operation.  The edge router 16 will have packet interfaces 52 capable of communicating with the associated media
gateways 18 and media gateway controller 22 as well as the routers 14 in the core network 12 as will be described below in greater detail.


 With reference to FIG. 6, assume the routers 14 in the core network 12 and the edge routers 16 cooperate to provide a multi-protocol label switching (MPLS) architecture.  In an MPLS architecture, labels are appended to data packets being
transferred from one edge router 16 to another via routers 14 in the core network 12.  The labels define a particular reserved path, which is a label-switched path (LSP) 54 in this embodiment, over which the data packet should travel from one edge router
16 to another.  In this embodiment, assume the edge routers 16 are label edge routers (LERs), and that the routers 14 in the core network 12 are label switch routers (LSRs).  When packets enter an MPLS architecture, the LERs look at the destination for
the packet and any other packet attributes and assign the packet a label.  The LERs then assign the data packet to a corresponding reserved path, such as LSP 54, and it is sent to a first LSR in the assigned LSP 54.  Each LSR along the LSP 54 will
forward the data packet along the LSP 54 based on the label, until the packet reaches a destination LER, which will remove the label and route the packet to an appropriate media gateway 18.


 As the packets travel along the LSP 54, the LSRs may simply monitor the label and forward the packet and label untouched, or may replace the label with a new label to facilitate routing or switching along the LSP 54.  Each LSR will include
routing tables based on the labels.  Thus, LSPs 54 extend between LERs, which are identified by labels.  The LERs assign, add, and remove labels as traffic enters or exits the MPLS architecture.  The MPLS architecture allows the establishment of LSPs 54
having a defined bandwidth reserved for the specified traffic source.  Those skilled in the art will be familiar with the concepts of establishing LSPs 54 in an MPLS architecture.  In the preferred embodiment, the LSPs 54 are provisioned by an operation
system or network provisioning tool based on constraints provided by the network operator.


 In one embodiment of the present invention, at least one LSP 54 is established between a first LER (edge router 16 in node 24A) and a second LER (edge router 16 in node 24B) as illustrated in FIG. 6.  The LSP 54 has a defined bandwidth and
provides controlled access.  A virtual packet-based trunk group is mapped to correspond to the LSP 54.  As such, the LSP 54 is engineered and provisioned with a guaranteed bandwidth matching the virtual trunk group size.  With reference to FIG. 7, the
thick shaded line overlaying the LSP 54 is representative of the virtual trunk group extending between the LERs provided by the edge routers 16.  Individual media flows 56 are set up dynamically by the media gateway controller 22 between the gateways 18
and the LERs provided by the edge routers 16.  Each individual media flow 56 represents a bi-directional communication.  The media gateways 18 will provide an interface between a traditional telephony interface associated with a telephone 20 or like
device and an individual media flow 56.


 The packets associated with individual media flows 56 are sent back and forth between the gateway 18 and the LER provided by the edge router 16.  Accordingly, the individual media flows 56 feed into a virtual trunk group supported by an LSP 54
at the LER provided by the edge router 16.  For example, individual real-time protocol (RTP) voice over IP streams generated at the media gateway 18 are sent to the LER and form a media flow 56.  The LER will assign a label to the packets forming the
media flow 56, and based on the label, route the packet to an LSR provided by a router 14 associated with the LSP 54.  In converse, packets coming in over a virtual trunk group from an LSP 54 into the LER will have their labels removed, and will be
routed over an individual media flow 56 to the appropriate media gateway 18, which will convert the packets into TDM streams, or the like, to facilitate telephony communications.  Thus, the individual media flows 56 together form a virtual trunk for
bi-directional communication and provide a virtual trunk group between routers 14 and through the core network 12.


 The individual media flows 56 on either side of the LSP 54 for a call are set up under the control of the media gateway controllers 22 using an appropriate call processing or media session control protocol, such as the session initiation
protocol for telephones (SIP-T) or Bearer Independent Call Control (BICC), which are familiar to those skilled in the art.  Thus, the media gateway controllers 22 will cooperate with each other or with call processing entities in the PSTN 26 to
facilitate a call between telephones 20 in different nodes 24.  Standard telephony interfaces are used between the telephones 20 and the gateways 18, wherein a packet-based media session is established between the respective gateways 18.


 Since the LSP 54 has a defined bandwidth and the virtual trunk group is designed to correspond to the LSP 54, the LSP 54 cannot use more bandwidth than originally allocated.  For example, if the virtual trunk group is set for 2000 channels, and
the bandwidth on the LSP 54 and all channels are used, the 2001.sup.st call will be blocked by the call processing of the media gateway controllers 22.  This prevents the LSP 54 from using more bandwidth than originally allocated to avoid violating
bandwidth contracts or suffering from degraded quality of service due to overloading.  Thus, once a virtual trunk group is fully used, the call processing provided by the media gateway controller 22 will block further calls.


 By associating the virtual trunk group with an LSP 54, the present invention assures quality of service levels over a packet network.  As illustrated in FIG. 8, LSPs 54 and corresponding virtual trunk groups can be configured between each of the
various LERs provided by the edge routers 16 to provide a comprehensive mesh throughout the core network 12.  To protect against link or device failures, backup LSPs 58, represented by dashed lines in FIG. 9, may be provided in case the primary LSPs 54
are unavailable.  The backup LSPs 58 are also engineered and provisioned with the maximum bandwidth required for the full virtual trunk group.  If a primary LSP 54 fails, the LER provided by the edge router 16 can automatically route the traffic to the
backup LSP 58.  The LSRs provided by the routers 14 in the core network 12 also have routing tables to facilitate the backup LSPs 58.  As such, call processing provided by the media gateway controllers 22 and the individual media flows 56 between the
gateways 18 and the edge routers 16 are unaffected and are not required to react to a failure, unless both the primary and backup LSPs 54, 58 fail for a given virtual trunk group.


 In another embodiment, instead of using a single LER, a pair of LERs may be used to increase network reliability, wherein a main LSP 54 terminates on one LER and a backup LSP 58 terminates on the second LER.  Those skilled in the art will
recognize the various combinations and flexibility provided with the implementation of a backup LSP 58 in association with a main LSP 54.


 In one embodiment of the present invention, a failure of an LSP 54 or backup LSP 58 may be quickly detected by sending heartbeat signals from the LER, such as those described under ITU-T Recommendation Y.1711--OAM mechanism for MPLS networks,
over the LSP 54 or backup LSP 58 at periodic intervals.  For example, if three heartbeats in a row are not received by the receiving LER, it will trigger a switchover to the backup LSP 58.  Again, the switchover is done independently of call processing. 
The heartbeat interval may be integrated as part of the heartbeat message itself.


 When both the primary and backup LSPs 54, 58 are operational, the LERs provided by the edge routers 16 can take steps to provide load sharing between the primary and backup LSPs 54, 58, in effect doubling the available bandwidth.  Load sharing
helps in reducing transport delay and jitter under normal conditions, and thus, improves overall quality.  Further, unused bandwidth may be used by lower-priority traffic.  The LERs may also be configured to take steps to prioritize and control traffic
based on a desired quality of service associated with the data being transferred.  The primary and backup LSPs 54, 58 are each composed of two unidirectional LSPs, one in each direction, providing bi-directional communication.  In the preferred
embodiment, each direction of the LSP 54, 58 will share the same links, routers 14, and nodes 24, instead of using potentially two different paths through the core network 12.  Bi-directional primary and backup LSPs 54, 58 will reduce the impact of an
LSP failure, as well as reduce the detection time of failures.  If both the primary and backup LSPs 54, 58 fail, the LER provided by the edge router 16 may inform the media gateway controller 22 that the LSP, and thus the associated virtual trunk group,
is no longer available.  The media gateway controller 22 then takes the virtual trunk group out of service and blocks calls requiring use of the failed LSPs 54, 58, or takes alternative action.


 In an alternative embodiment, the core network 12 may include ATM switches wherein the reserved bandwidth path is implemented via permanent virtual circuits (PVCs) that may be established between two edge ATM switches through the core network
12.  Like the LSPs, the PVCs are engineered and provisioned with a guaranteed bandwidth, which corresponds to a virtual trunk group.  PVCs will typically carry a set number of packet streams of voice over IP (VoIP), voice over ATM (VoATM), or the like. 
Call processing, backup reserve paths, and failure detection may take place as described above.


 Typically, call processing takes place on a call-by-call basis, wherein channels associated with a call are allocated on a channel-by-channel basis.  A call processing counter may be implemented to keep track of the number of channels being used
or remaining available in light of the reserved bandwidth associated with the LSP 54 or virtual trunk group.  If the call processing counter reaches a maximum, a fast busy signal may be provided to indicate that all circuits are busy, thereby preventing
violation of bandwidth contracts or degradation in quality of service.


 Thus, reserved paths are established between the edge routers 16 with which virtual trunk groups are associated.  The bandwidth for the reserved path in the associated virtual trunk group coincides to ensure quality of service levels over the
core network 12.  The reserved paths may be formed using various architectures, including MPLS and PVCs.


 With reference to FIG. 10, an access node 10 is associated with the local network 4 to facilitate communications with other local networks 4 via the central network 6.  The access node 10 includes a local edge router 60, which is similar to edge
routers 16, and call controller 62, which facilitates call control similar to the media gateway controllers 22.  Within the local network 4, the access node 10 facilitates the routing of packets to and from the edge routers 16 within the local network 4
via the routers 14 (FIG. 2) and to and from entities on the other local networks 4 via the inter-network reserved paths 8 under the control of the call controller 62.  In essence, the local edge router 60 is the ingress and egress point for packets
between the local network 4 and the central network 6 and operates under control of the call controller 62.


 The local edge router 60 is virtually connected to each of the edge routers 16 in the associated core network 12 via LSPs 54A configured just as the LSPs 54, which interconnect the edge routers 16.  Similarly, the LSPs 54A have a defined
bandwidth and provide controlled access.  A virtual, packet-based trunk group is mapped to correspond to the LSPs 54A.  As such, the LSPs 54A are engineered and provisioned with a guaranteed bandwidth matching the virtual trunk group size.  The thick
shaded lines overlaying the LSPs 54A are representative of the virtual trunk group extending between the local edge router 60 and the edge routers 16.  Notably, the local edge router 60, just like the edge routers 16, is an LER in an MPLS architecture.


 Media flows are set up dynamically by the call controller 62 and the media gateway controllers 22 between the LER provided by the local edge router 60 and the LERs provided by the edge routers 16.  Corresponding media flows are set up
dynamically by call controllers 62 of the various access nodes 10 between the LERs provided by the local edge routers 60 of the respective access nodes 10 via the central network's inter-network reserved paths 8, which are LSPs providing virtual trunk
groups.  Each media flow provides bi-directional communication.  In essence, the local edge routers 60 will establish media flows between an LSP 54A of the local network 4 and LSPs of the central network 6 for calls between local networks 4.  The media
flows will feed into virtual trunk groups provided by the respective LSPs in the local network 4 and the central network 6.  The media flows are set up by the call controller 62 and media gateway controllers 62 using an appropriate call processing or
media session control protocol.


 FIG. 11 is a block schematic of a local edge router 60 having a CPU 64 with associated memory 66 and the requisite software 68 for operation.  The local edge router 60 will have packet interfaces 70 capable of communicating with the associated
call controller 62 as well as with the routers 14 in the core network 12 and entities, including routers, in the central network 6.


 Referring now to FIG. 12, a block schematic of a call controller 62 is shown having a CPU 72 containing memory 74 and the requisite software 76 for operation.  The call controller 62 will have at least one interface, preferably a packet
interface 78 capable of communicating with other call controllers 62, media gateway controllers 22, and the LERs provided by the local edge router 60 and the edge routers 16.  To establish such communications, the call controllers 62 and media gateway
controllers 22 cooperate to establish the media flows via the virtual trunk groups.


 Turning now to FIG. 13, the central network 6 includes numerous routers 80 interconnected to facilitate the routing of packets between the local edge routers 60 of the access nodes 10 in the local networks 4.  As noted, the local edge routers 60
act as the ingress and egress points between the local networks 4 and the central network 6.


 As with the local networks, assume the routers 80 in the central network 6 and the local edge routers 60 also cooperate to provide an MPLS architecture.  As such, assume the local edge routers 60 are label edge routers (LERs), and the routers 80
in the central network 6 are label switch routers (LSRs).  For routing, the LERs provided by the local edge routers 60 look at the destination for the packet and any other packet attributes and assign the packet a label.  The LERs then assign the data
packet to a corresponding reserved path, LSP (8), and it is sent to a first LSR (80) in the assigned LSP (8).  Each LSR (80) along the LSP (8) will forward the data packet along the LSP (8) based on the label, until the packet reaches a destination LER,
which will remove the label and repeat the process to route the packet to an appropriate label edge router 16 in the respective local network 4.


 As the packets travel along the LSP (8), the LSRs may simply monitor the label and forward the packet and label untouched, or may replace the label with a new label to facilitate routing or switching along the LSP (8).  Each LSR (80) will
include routing tables based on the labels.  The LERs provided by the local edge routers 60 assign, add, and remove labels as traffic enters or exits the MPLS architecture.  The LSPs (8) have a defined bandwidth reserved for the specified traffic source. Those skilled in the art will be familiar with the concepts of establishing LSPs (8) in an MPLS architecture.  In the preferred embodiment, The LSPs (8) of the central network 6 are provisioned by an operating system or network provisioning tool based on
constraints provided by the network operator, just as those for the LSPs 54, 54A in the local networks 4.


 As depicted, LSPs (8) connect each of the LERs provided by the local edge routers 60.  The LSP (8) has a defined bandwidth and provides controlled access.  A virtual, packet-based trunk group is mapped to correspond to the LSP (8).  As such, the
LSP (8) is engineered and provisioned with a guaranteed bandwidth matching the virtual trunk group size.  The thick shaded lines overlaying the LSPs (8) represent the virtual trunk groups extending between the LERs provided by the edge routers 60.


 The packets associated with media flows are sent back and forth between the respective edge routers 16 and the local edge router 60 in local trunk groups.  The individual media from the local trunk group feeds into a central trunk group
supported by an LSP (8) at the local edge routers 60.  The local edge router 60 will re-assign a label to the packets forming the media flow, and based on the new label, route the packet to an LSR provided by a router 80 associated with the LSP (8) in
the central network 6.  In converse, packets coming in over a virtual trunk group from an LSP (8) into the local edge router 60 will have their labels removed, and will have new labels assigned prior to being routed over an LSP 54A to the appropriate
edge router 16.  The media flows on either side of the LSP (8) for a call are set up under the control of the call controllers 62 using an appropriate call processing or media session control protocol.


 Since the LSP (8) has a defined bandwidth and the virtual trunk group is designed to correspond to the LSP (8), the LSP (8) cannot use more bandwidth than originally allocated.  This prevents the LSP (8) from using more bandwidth than originally
allocated to avoid violating bandwidth contracts or suffering from degraded quality of service due to overloading.  Thus, once a virtual trunk group is fully used, the call processing provided by the call controller 62 will block further calls.


 By associating the virtual trunk group with an LSP (8), the present invention assures quality of service levels over a packet network.  As illustrated, LSPs (8) and corresponding virtual trunk groups can be configured between each of the various
LERs provided by the local edge routers 60, to provide a comprehensive mesh throughout the central network 6.  To protect against link or device failures, backup LSPs 82, represented by dashed lines in FIG. 14, may be provided in case the primary LSPs
(8) are unavailable.  The backup LSPs 82 are also engineered and provisioned with the maximum bandwidth required for the full virtual trunk group.  If a primary LSP (8) fails, the LER provided by the local edge router 60 can automatically route the
traffic to the backup LSP 82.  The LSRs provided by the routers 80 in the central network 6 also have routing tables to facilitate the backup LSPs 82.  As such, call processing provided by the call controllers 62 is unaffected and not required to react
to a failure, unless both the primary and backup LSPs (8), 82 fail for a given virtual trunk group.


 As within the local networks 4, instead of using a single local edge router 60, a pair of local edge routers 60 may be used to increase network reliability, wherein a main LSP (8) terminates on one local edge router 60 and a backup LSP 82
terminates on the second local edge router 60.  Those skilled in the art will recognize the various combinations and flexibility provided with the implementation of a backup LSP 82 in association with a main LSP (8).  Further, a failure of an LSP (8) or
backup LSP 82 may be quickly detected by sending heartbeat signals.  When a desired number of heartbeats in a row are not received by the receiving LER, it will trigger a switchover to the backup LSP 82.  The switchover is done independently of call
processing.  The heartbeat interval may be integrated as part of the heartbeat message itself.


 When both the primary and backup LSPs (8), 82 are operational, the LERs provided by the local edge routers 60 can take steps to provide load sharing between the primary and backup LSPs (8), 82, in effect doubling the available bandwidth. 
Further, unused bandwidth may be used by lower-priority traffic.  The LERs may also be configured to take steps to prioritize and control traffic based on a desired quality of service associated with the data being transferred.  The primary and backup
LSPs (8), 82 are each composed of two unidirectional LSPs, one in each direction, providing bi-directional communication.  As with the local networks 4, each direction of the LSP (8), 82 will share the same links, routers 80, and local edge routers 60,
instead of using potentially two different paths through the central network 6.  Bi-directional primary and backup LSPs (8), 82 will reduce the impact of an LSP failure, as well as reduce the detection time of failures.  If both the primary and backup
LSPs (8), 82 fail, the LER provided by the local edge router 60 may inform the call controller 62 that the LSP, and thus the associated virtual trunk group, is no longer available.  The call controller 62 then takes the virtual trunk group out of service
and blocks calls requiring use of the failed LSPs (8), 82, or takes alternative action.


 In an alternative embodiment, the central network 6 may include ATM switches wherein the reserved bandwidth path is implemented via permanent virtual circuits (PVCs) that may be established between two edge ATM switches through the central
network 6.  Like the LSPs, the PVCs are engineered and provisioned with a guaranteed bandwidth, which corresponds to a virtual trunk group.  PVCs will typically carry a set number of packet streams of voice over IP (VoIP), voice over ATM (VoATM), or the
like.  Call processing, backup reserve paths, and failure detection may take place as described above.


 As with the local networks 4, call processing may take place on a call-by-call basis, wherein channels associated with a call are allocated on a channel-by-channel basis.  A call processing counter may be implemented to keep track of the number
of channels being used or remaining available in light of the reserved bandwidth associated with the LSP (8) or virtual trunk group.  If the call processing counter reaches a maximum, a fast busy signal may be provided to indicate that all circuits are
busy, thereby preventing violation of bandwidth contracts or degradation in quality of service.


 Thus, reserved paths are established between the local edge routers 60 with which virtual trunk groups are associated.  The bandwidth for the reserved path in the associated virtual trunk group coincides to ensure quality of service levels over
the central network 6.  The reserved paths may be formed using various architectures, including MPLS and PVCs in both local networks 4 and central networks 6 connecting the local networks 4.


 The invention provides for a hierarchical network infrastructure wherein a network of reserved paths may be established at each network level, and access between network levels is provided by an access node that terminates reserved paths on the
connection networks.  As such, the infrastructure is infinitely scalable and may support two or more network layers in an efficient and easy to manage manner.  Thus, although the above disclosure discusses only two network layers, the central and local
network layers, additional network layers may be provided below the local network layer and above the central network layers, wherein multiple central networks may terminate to a common network.


 Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present invention.  All such improvements and modifications are considered within the scope of the concepts disclosed herein and the
claims that follow.


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DOCUMENT INFO
Description: The present invention relates to telecommunications, and in particular to ensuring quality of service levels over packet networks.BACKGROUND OF THE INVENTION There is a growing interest in the convergence of the public switched telephone network (PSTN), the Internet and other internets and intranets. The convergence of these networks requires technology that facilitates interworking in a uniform andeffective manner. The next generation of unified networks will provide an open and scalable architecture to accommodate multiple vendors and protocols under a common packet network. At the moment, there are several obstacles to providing telephonyservices on a packet network with the same level of performance and availability as is available on the PSTN today. The traditional PSTN provides constant bandwidth streams of information between users. These media streams travel over dedicated circuits. On the other hand, packet networks have been prone to packet loss and delays, which affect the qualityof streaming media required to carry voice communications. Given the high quality levels associated with the PSTN, subscribers expect and demand traditional quality regardless of the transmission medium. The bursty nature of packet communications makes controlling communication quality and ensuring sufficient bandwidth very difficult. The bursty nature of packet communications makes controlling communication quality and ensuring sufficient bandwidth very difficult. Traditional "fat pipe" models, which rely on the overall network to find a way to transmit the packets with therequired quality of service levels, have not been completely successful. Further, the integration of call processing for the PSTN and packet networks has proven difficult to manage. Given the desire to use packet networks as the centerpiece for telephony communications, there is a need for a way to ensure quality of service levels for telephony communication carried at least in part over packet networ